C-arm C-arm Computed Tomography Research Articles

Role of C-Arm CT in Identifying Caudate Arteries Supplying Hepatocellular Carcinoma

PurposeTo evaluate the role of C-arm computed tomography (CT) performed at the proper hepatic artery or equivalent in patients with caudate-lobe hepatocellular carcinoma (HCC) for the detection of tumor-feeding arteries during chemoembolization. Materials and MethodsFrom July 2009 to June 2012, 1,785 patients received initial chemoembolization at a single institution. Among them, 52 patients with caudate HCC underwent initial chemoembolization with the use of C-arm CT. C-arm CT images were obtained at the proper hepatic artery or equivalent. Two radiologists reviewed the C-arm CT scans and angiograms in consensus. The cumulative local recurrence rate was calculated by the Kaplan–Meier method. ResultsTumor-feeding arteries were single (n = 31), double (n = 12), triple (n = 6), and quadruple (n = 3). Seventy-nine tumor-feeding arteries and their origins in 48 patients were demonstrated on C-arm CT. In four patients (7.7%), five tumor-feeding arteries were not clearly indicated on C-arm CT because of poor image quality caused by failure of the patients to hold their breath. Selective chemoembolization via tumor-feeding arteries was successful in 45 patients (87%). The cumulative local recurrence rates at 6 months, 1 year, and 3 years were 19.4%, 32.8%, and 35.8%, respectively. Nonselective chemoembolization of tumor-feeding arteries of caudate-lobe HCC was a significantly important factor in higher cumulative local recurrence rates (hazard ratio, 3.916; 95% confidence interval, 1.367–11.216; P = .011). ConclusionC-arm CT obtained at the proper hepatic artery or equivalent level can demonstrate most tumor-feeding arteries supplying HCCs in the caudate lobe.

Value of C-arm computed tomography in radiofrequency ablation of small lung lesions.

This study aimed to explore the value of C-arm computed tomography (CT) applications in radiofrequency ablation (RFA) of small lung lesions. The puncture success rate, cumulative survival rate, tumor response rate, complications, and radiation dose during C-arm CT-guided RFA of 36 small lung lesions in 34 patients were analyzed. In 35 RFA procedures for 36 small lung lesions, the puncture success rate was 100%. There were 7 cases of complications, including 4 cases of pneumothorax (puncture suction or closed chest drainage was not required) and 3 cases of hemoptysis. The cumulative survival rate in the 34 patients after RFA was 100% at 6 months, 69.0% at 1 year, and 60.0% at 2 years. In assessments of 36 foci imaged during the follow-up period, the total response rates at 1 month, 3 months, and 6 months were 77.8% (28/36), 69.7% (23/33), and 61.3% (19/31), respectively. The mean cumulative dose and average effective dose during surgery were 120.1 ± 61.4 mGy and 3.5 ± 1.7 mSv, respectively. The application of C-arm CT to RFA of small lung lesions could provide abundant information to the surgeon and increase the lesion puncture success rate and is considered to be a promising image-guided technology.

Carbon Dioxide Contrast Enhancement for C-Arm CT Utility for Treatment Planning during Hepatic Embolization Procedures

A pilot study was performed to evaluate the use of carbon dioxide (CO2) as a contrast medium for C-arm computed tomography (CT). C-arm CT using CO2 was performed during embolization procedures in12 patients with hepatic malignancies and severe iodine allergy or high risk for nephrotoxicity. C-arm CT using gadolinium or iodinated contrast medium was performed for comparison. Of segmental arteries identified by conventional contrast enhancement, 96% were also seen with CO2 enhancement, but subsegmental arteries were not reliably depicted. CO2 enhancement identified 60% of tumors. Small, hypovascular, and infiltrative tumors were difficult to detect. CO2 is a promising alternative intraarterial contrast agent for C-arm CT.

Clinical utility and limitations of tumor-feeder detection software for liver cancer embolization

PurposeTo evaluate the clinical utility and limitations of a computer software program for detecting tumor feeders of hepatocellular carcinoma (HCC) during transarterial chemoembolization (TACE). Materials and methodsForty-six patients with 59 HCC nodules underwent nonselective digital subtraction angiography (DSA) and C-arm computed tomography (CT) in the same hepatic artery. C-arm CT data sets were analyzed using the software to identify potential tumor feeders during each TACE session. For DSA analysis, 3 radiologists were independently assigned to identify tumor feeders using the DSA images in a separate session. The sensitivity of the 2 techniques in detecting tumor feeders was compared, with TACE findings as the reference standard. Factors affecting the failure of the software to detect tumor feeders were assessed by univariate and multivariate analyses. ResultsWe detected 65 tumor feeders supplying 59 HCC nodules during TACE sessions. The sensitivity of the software to detect tumor feeders was significantly higher than that of the manual assessment using DSA (87.7% vs. 71.8%, P<0.001). Multivariate analysis showed that a tumor feeder diameter of <1.0mm (hazard ratio [HR], 56.3; P=0.003) and lipiodol accumulation adjacent to the tumor (HR, 11.4; P=0.044) were the significant predictors for failure to detect tumor feeders. ConclusionThe software analysis was superior to manual assessment with DSA in detecting tumor feeders during TACE for HCC. However, the capability of the software to detect tumor feeders was limited by vessel caliber and by prior lipiodol accumulation to the tumor.

Angiographic C-arm CT visualization of the Woven EndoBridge Cerebral Aneurysm Embolization Device (WEB): First Experience in an Animal Aneurysm Model

Improvements in the imaging capabilities of angiographic C-arm computed tomography (CT) using flat detector angiographic (FD-CT) systems now provide a means for the in vivo visualization of devices used for the treatment of intracranial aneurysms. One such device, the WEB embolization device, is made of a braided mesh of nitinol wires, the size of which are near to the limits of visualization using conventional x-ray fluoroscopy. Our hypothesis was that the imaging of these implants C-arm CT would provide useful information regarding their positioning and deployment. In five New Zealand white rabbits elastase induced aneurysms were created and subsequently treated using a WEB. Imaging was performed using digital subtraction angiography (DSA), X-ray imaging and two different Angiographic C-arm CT protocols. The images were evaluated by two neuroradiologists using an evaluation scale. The mesh of the WEB was barely visible on the DSA or x-ray fluoroscopy images. Volume rendering technique (VRT) reconstruction and multiplanar reconstruction (MPR) of images done using the C-arm CT protocols clearly delineated the shape and structure of the device. Contrast-enhanced MPR and VRT reconstructions allowed assessment of the status of blood flow in the aneurysms. Beam hardening artifacts caused by platinum markers on the WEB were present. In vivo C-arm CT imaging of the WEB is feasible and allows precise determination of the position and deployment status of the device. On contrast-enhanced images the occlusion status of aneurysms and the positioning of the WEB in relationship to the parent artery can be evaluated. C-arm-CT may serve as a minimal-invasive follow-up imaging modality.

Intraoperative C-arm CT imaging in angular stable plate osteosynthesis of distal radius fractures

The purpose of this study was to analyze the practicability and benefit of intraoperative C-arm computed tomography (CT) imaging in volar plate osteosynthesis of unstable distal radius fractures. During a 1 year period, intraoperative three dimensional (3D) imaging with the ARCADIS Orbic 3D was performed in addition to standard fluoroscopy in 51 cases. The volar angular stable plate oesteosyntheses were analyzed intraoperatively and, if necessary, improved immediately. The duration of the scan and radiation exposure dose were measured. On average, performance of the scan and analysis of the CT dataset took 6.7 minutes. In 31.3% of the surgeries a misplacement of screws was detected and correction was done immediately. C-arm CT imaging can easily be integrated in the normal course of surgery. As a complement to the standard 2D-fluoroscopy, the C-arm CT is a useful tool to evaluate the quality of osteosynthesis.

Percutaneous Punctures with MR Imaging Guidance: Comparison between MR Imaging–enhanced Fluoroscopic Guidance and Real-time MR Imaging Guidance

To evaluate and compare the technical accuracy and feasibility of magnetic resonance (MR) imaging-enhanced fluoroscopic guidance and real-time MR imaging guidance for percutaneous puncture procedures in phantoms and animals. The experimental protocol was approved by the institutional animal care and use committee. Punctures were performed in phantoms, aiming for markers (20 each for MR imaging-enhanced fluoroscopic guidance and real-time MR imaging guidance), and pigs, aiming for anatomic landmarks (10 for MR imaging-enhanced fluoroscopic guidance and five for MR imaging guidance). To guide the punctures, T1-weighted three-dimensional (3D) MR images of the phantom or pig were acquired. Additional axial and coronal T2-weighted images were used to visualize the anatomy in the animals. For MR imaging-enhanced fluoroscopic guidance, phantoms and pigs were transferred to the fluoroscopic system after initial MR imaging and C-arm computed tomography (CT) was performed. C-arm CT and MR imaging data sets were coregistered. Prototype navigation software was used to plan a puncture path with use of MR images and to superimpose it on fluoroscopic images. For real-time MR imaging, an interventional MR imaging prototype for interactive real-time section position navigation was used. Punctures were performed within the magnet bore. After completion, 3D MR imaging was performed to evaluate the accuracy of insertions. Puncture durations were compared by using the log-rank test. The Mann-Whitney U test was applied to compare the spatial errors. In phantoms, the mean total error was 8.6 mm ± 2.8 with MR imaging-enhanced fluoroscopic guidance and 4.0 mm ± 1.2 with real-time MR imaging guidance (P < .001). The mean puncture time was 2 minutes 10 seconds ± 44 seconds with MR imaging-enhanced fluoroscopic guidance and 37 seconds ± 14 with real-time MR imaging guidance (P < .001). In the animal study, a tolerable distance (<1 cm) between target and needle tip was observed for both MR imaging-enhanced fluoroscopic guidance and real-time MR imaging guidance. The mean total error was 7.7 mm ± 2.4 with MR imaging-enhanced fluoroscopic guidance and 7.9 mm ± 4.9 with real-time MR imaging guidance (P = .77). The mean puncture time was 5 minutes 43 seconds ± 2 minutes 7 seconds with MR imaging-enhanced fluoroscopic guidance and 5 minutes 14 seconds ± 2 minutes 25 seconds with real-time MR imaging guidance (P = .68). Both MR imaging-enhanced fluoroscopic guidance and real-time MR imaging guidance demonstrated reasonable and similar accuracy in guiding needle placement to selected targets in phantoms and animals.

Carbon Dioxide (CO2) vs Iodinated Contrast Digital Subtraction Angiography during Balloon-occluded Retrograde Transvenous Obliteration (BRTO) Using Foam Sclerosant for Gastric Varices

PurposeTo compare the visualization of the target gastric varices (GV) on balloon-occluded retrograde transvenous venography (BRTV) using iodinated contrast material vs carbon dioxide (CO2) in preparation for subsequent balloon-occluded retrograde transvenous obliteration (BRTO) using foam sclerotherapy. Materials and MethodsIn 16 consecutive patients with nonruptured GV, BRTV was performed first using iodinated contrast material and then with CO2. BRTV was repeated whenever there were changes in the catheter or patient position or when coil embolization of collaterals was needed. Each visualization grade of GV (grade 1=GV only; grade 2=GV >collaterals; 3=GV<collaterals; grades 4–5=collaterals only) was determined by two observers in consensus. During foam BRTO, the GV visualization grade was recorded again and confirmed by C-arm computed tomography (CT). ResultsIn 38 pairs of BRTV, GV grades were significantly (P<.0001) lower (ie, favoring BRTO) on CO2 BRTV (mean±standard deviation, 1.8±0.8) than on iodine BRTV (3.4±0.8). GV grades on foam BRTO (1.4±0.7) were similar to the grades obtained on the most recent CO2 BRTV (1.3±0.5) but were significantly smaller (P<.0001) than on iodinated BRTV (3.1±0.9). GV were opacified by foam on initial C-arm CT in 14 patients (87.5%), and complete thrombosis of GV was obtained without any complication in all 16 patients (100%). CO2 reached the GV even when iodinated contrast material could not (grade 4) in seven of our 16 patients (43.8%), leading to successful BRTO. ConclusionsCO2 BRTV visualized GV better than did iodine BRTV and changed the management of more than 40% of patients by enabling successful foam BRTO in patients in which conventional liquid BRTO could not be performed.

Fusion of intravenous contrast-enhanced C-arm CT and pretreatment imaging for ablation margin assessment of liver tumors: A preliminary study

The aim of this preliminary study was to evaluate the feasibility of assessing ablation margins after radiofrequency ablation (RFA) of liver tumors from fusion images of post-treatment C-arm computed tomography (CT) images fused to pretreatment images. Five patients with liver tumors underwent RFA. Intravenous contrast-enhanced C-arm CT images were obtained for all patients immediately after RFA, and multi-detector CT (MDCT) images were obtained 3-7 days later. The C-arm CT and MDCT images were fused to pretreatment images using a multimodality image fusion software. The minimum ablation margins were assessed in the C-arm CT and MDCT fusion images. Ablation margins after RFA of liver tumors can be measured using intravenous contrast-enhanced C-arm CT images fused with pretreatment images. This technique has the potential for use in the intra-procedural assessment of liver tumor ablation.

Survival after C-arm CT-assisted chemoembolization of unresectable hepatocellular carcinoma

PurposeTo compare patient survival after transarterial chemoembolization with and without intraprocedural C-arm computed tomography (CT) in patients with unresectable hepatocellular carcinoma. Materials and methodsWe retrospectively reviewed the records of 130 patients with unresectable hepatocellular carcinoma who underwent lipiodol-based chemoembolization using a C-arm cone-beam system. We compared patients who underwent chemoembolization with angiography alone (69 patients; April 2005–July 2007) to those who underwent C-arm CT-assisted chemoembolization (61 patients; July 2007–April 2010). Overall and local progression-free survivals were compared using the Kaplan–Meier estimator with log-rank testing. Univariate and multivariate analyses were performed using the Cox proportional hazards model. ResultsOverall survival rates of patients who underwent chemoembolization with and without C-arm CT assistance were 94% and 79%, 81% and 65%, and 71% and 44% at 1, 2, and 3 years, respectively. Local progression-free survival rates of these patients were 43% and 27%, 31% and 10%, and 26% and 5% at 1, 2, and 3 years, respectively. Patients receiving C-arm CT-assisted chemoembolization had significantly higher overall (P=0.005) and local progression-free (P=0.003) survival rates than those receiving chemoembolization with angiography alone. Multivariate analysis showed that C-arm CT assistance was an independent factor associated with longer overall survival (hazard ratio, 0.40; P=0.033) and local progression-free survival (hazard ratio, 0.25; P=0.003). ConclusionC-arm CT usage in addition to angiography during transarterial chemoembolization prolongs survival in patients with unresectable hepatocellular carcinoma.

Automatic Aorta Segmentation and Valve Landmark Detection in C-Arm CT for Transcatheter Aortic Valve Implantation

Transcatheter aortic valve implantation (TAVI) is a minimally invasive procedure to treat severe aortic valve stenosis. As an emerging imaging technique, C-arm computed tomography (CT) plays a more and more important role in TAVI on both pre-operative surgical planning (e.g., providing 3-D valve measurements) and intra-operative guidance (e.g., determining a proper C-arm angulation). Automatic aorta segmentation and aortic valve landmark detection in a C-arm CT volume facilitate the seamless integration of C-arm CT into the TAVI workflow and improve the patient care. In this paper, we present a part-based aorta segmentation approach, which can handle structural variation of the aorta in case that the aortic arch and descending aorta are missing in the volume. The whole aorta model is split into four parts: aortic root, ascending aorta, aortic arch, and descending aorta. Discriminative learning is applied to train a detector for each part separately to exploit the rich domain knowledge embedded in an expert-annotated dataset. Eight important aortic valve landmarks (three hinges, three commissures, and two coronary ostia) are also detected automatically with an efficient hierarchical approach. Our approach is robust under all kinds of variations observed in a real clinical setting, including changes in the field-of-view, contrast agent injection, scan timing, and aortic valve regurgitation. Taking about 1.1 s to process a volume, it is also computationally efficient. Under the guidance of the automatically extracted patient-specific aorta model, the physicians can properly determine the C-arm angulation and deploy the prosthetic valve. Promising outcomes have been achieved in real clinical applications.

Optimization of acquisition and contrast injection protocol for C-arm CT imaging in transcatheter aortic valve implantation: initial experience in a swine model

To determine the optimal C-arm computed tomography (CT) protocol for transcatheter aortic valve implantation (TAVI) in swine. In 6 swine, C-arm CT was performed using 5-s ungated acquisition during sinus rhythm with aortic root (Method 1) or peripheral (Method 2) injection, and during rapid ventricular pacing with root injection (Method 3). Additionally, 24-s ECG-gated acquisitions were performed during sinus rhythm with root (Method 4) or peripheral (Method 5) injection. Aortic root enhancement, presence of artifacts and contrast volumes were compared for all methods. Aortic root measurements were also compared between C-arm CT and multidetector-row computed tomography (MDCT). The best C-arm CT image set was identified and used to predict optimal angiographic projection angles during TAVI; predictions were compared to those from MDCT. Methods 1, 3, 4, and 5 yielded sufficient root enhancement with mild or moderate artifacts and aortic annulus, sinotubular junction, and mid-ascending aorta diameters similar to MDCT. Ungated C-arm CT (Methods 1, 3) required less contrast than ECG-gated C-arm CT (Methods 4, 5). Method 3 was optimal yielding images with high attenuation, few artifacts (2.0), and root measurements similar to MDCT using minimal contrast (36 mL). Predicted angiographic projections from Method 3 were similar to MDCT. Ungated C-arm CT during rapid pacing with aortic root injection required minimal contrast, yielded high attenuation and few artifacts, and aortic root measurements and predicted angiographic planes similar to those from MDCT.

Invited commentary

Although in use for digital subtraction angiography (DSA) since about the 1970s,1Hawkins I.F. Carbon dioxide digital subtraction arteriography.AJR Am J Roentgenol. 1982; 139: 19-24Crossref PubMed Scopus (158) Google Scholar carbon dioxide remains a very useful contrast medium in our ever-growing population of patients with renal insufficiency and/or significant iodinated-contrast sensitivity. With the present report, Criado et al add to the existing support for use of CO2 DSA in endovascular aortic aneurysm repair (EVAR). Providing support for alternate imaging methods to deliver endovascular therapy safely is particularly important, considering improving technologies will extend therapy to more patients who are at risk of renal compromise. As others have,2Chao A. Major K. Kumar S.R. Patel K. Trujillo I. Hood D.B. et al.Carbon dioxide digital subtraction angiography-assisted endovascular aortic aneurysm repair in the azotemic patient.J Vasc Surg. 2007; 45: 451-458Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar, 3Bush R.L. Lin P.H. Bianco C.C. Lumsden A.B. Gunnoud A.B. Terramani T.T. et al.Endovascular aortic aneurysm repair in patients with renal dysfunction or severe contrast allergy: utility of imaging modalities without iodinated contrast.Ann Vasc Surg. 2002; 16: 537-544Abstract Full Text PDF PubMed Scopus (39) Google Scholar, 4Lee A.D. Hall R.G. An evaluation of the use of carbon dioxide angiography in endovascular aortic aneurysm repair.Vasc Endovasc Surg. 2010; 44: 341-344Crossref PubMed Scopus (19) Google Scholar Criado et al demonstrate that CO2 DSA is safe, and results are comparable with procedures performed with iodinated contrast. The single element that sets this paper apart from previous ones is that radiation times were shorter for CO2 than iodinated contrast; this is inexplicable based even on our own experience. Furthermore, settings are modified for CO2 DSA by increasing the frame rate, a maneuver that tends to increase the radiation dose. In their paper, the authors conclude with a rhetorical question; why should procedures be performed with iodinated contrast if results are equivalent? There are multiple reasons for this: 1) as CO2 is delivered by hand injection, there is significant potential for increased radiation exposure as the interventionalist is always at the table, and this becomes even more relevant if indeed the radiation times are longer as described by previous authors. 2) The potential for complications with air emboli is also increased by the fact that no system is completely sealed; the plastic bag system (AngioFlush 111, AngioDynamics, Queensbury, NY) is being discontinued due to a Food and Drug Administration mandate following a serious complication, where the bag was filled with O2 rather than CO2.5Cho K.J. Hawkins Jr, I.F. Discontinuation of the plastic bag delivery system for carbon dioxide angiography will increase radiocontrast nephropathy and life-threatening complications.AJR Am J Roentgenol. 2011; 197: W940-W941Crossref PubMed Scopus (4) Google Scholar There is some instruction and expertise required to avoid potentially serious complications. 3) In order to prevent overestimating disease, when injecting in the aorta a bolus of 40 to 60 mL of CO2 is required, which can lead to “trapping” of CO2 within a branch, ultimately leading to ischemic insult. This can be somewhat mitigated by patient positioning, but only experience or adequate instruction will prompt such maneuvers.6Spinosa D.J. Matsumoto A.H. Angle J.F. Hagspiel K.D. Hooper T.N. Transient mesenteric ischemia: a complication of carbon dioxide angiography.J Vasc Interv Radiol. 1998; 9: 561-564Abstract Full Text PDF PubMed Scopus (39) Google Scholar In a larger review of cases, complication rates were minor in 7% and major in 1.1% of cases.7Rundback J.H. Shah P.M. Wong J. Babu S.C. Rozenblit G. Poplausky M.R. Livedo reticularis, rhabdomyolysis, massive intestinal infarction, and death after carbon dioxide arteriography.J Vasc Surg. 1997; 26: 337-340Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar The authors briefly described alternate imaging modalities such as intravascular ultrasound (IVUS), but did not include another very valuable way of avoiding contrast, by performing preoperative magnetic resonance angiography (MRA). This MRA can be imported into a system capable of c-arm computed tomography (CT) image acquisition (dynaCT, XperCT). The imported image is thereafter fused with the c-arm CT acquisition and can then serve as a 3D overlay, which can precisely guide the EVAR. Furthermore, it is important to consider that the operative phase is only a small segment of what is a lifetime of imaging for patients with EVAR. In the pre- and postoperative phase, it is imperative that we continue to keep the patients from iodinated contrast exposure and perform studies either with MR (depending on stent), noncontrast CT, or by ultrasound either with or without contrast enhancement. Endovascular aortic aneurysm repair with carbon dioxide-guided angiography in patients with renal insufficiencyJournal of Vascular SurgeryVol. 55Issue 6PreviewRenal dysfunction following endovascular abdominal aortic aneurysm repair (EVAR) remains a significant source of morbidity and mortality. We studied the use of carbon dioxide (CO2) as a non-nephrotoxic contrast agent for EVAR. Full-Text PDF Open Archive

Ablation margin assessment of liver tumors with intravenous contrast-enhanced C-arm computed tomography

To evaluate the feasibility of intravenous contrast-enhanced C-arm computed tomography (CT) for assessing ablative areas and margins of liver tumors. Twelve patients (5 men, 7 women; mean age, 69.5 years) who had liver tumors (8 hepatocellular carcinomas, 4 metastatic liver tumors; mean size, 16.3 mm; size range, 8-20 mm) and who underwent percutaneous radiofrequency ablations (RFAs) with a flat-detector C-arm system were retrospectively reviewed. Intravenously enhanced C-arm CT and multidetector computed tomography (MDCT) images were obtained at the end of the RFA sessions and 3-7 d after RFA to evaluate the ablative areas and margins. The ablated areas and margins were measured using axial plane images acquired by both imaging techniques, with prior contrast-enhanced MDCT images as the reference. The sensitivity, specificity, and positive and negative predictive values of C-arm CT for detecting insufficient ablative margins (< 5 mm) were calculated. Statistical differences in the ablative areas and margins evaluated with both imaging techniques were compared using a paired t-test. All RFA procedures were technically successful. Of 48 total ablative margins, 19 (39.6%) and 20 (41.6%) margins were found to be insufficient with C-arm CT and MDCT, respectively. Moreover, there were no significant differences between these 2 imaging techniques in the detection of these insufficient ablative margins. The sensitivity, specificity, and positive and negative predictive values for detecting insufficient margins by C-arm CT were 90.0%, 96.4%, 94.7% and 93.1%, respectively. The mean estimated ablative areas calculated from C-arm CT (462.5 ± 202.1 mm(2)) and from MDCT (441.2 ± 212.5 mm(2)) were not significantly different. The mean ablative margins evaluated by C-arm CT (6.4 ± 2.2 mm) and by MDCT (6.0 ± 2.4 mm) were also not significantly different. The efficacy of intravenous contrast-enhanced C-arm CT in assessing the ablative areas and margins after RFA of liver tumors is nearly equivalent to that of MDCT.

Effective dose to patient during neuroradiological procedures of c-arm CT

We aimed to determine the effective dose given to patients during neuroradiological C-arm computed tomography (CT) procedures. Measurements were performed on 48 patients using a dose-area product (DAP) meter. A PC-based Monte Carlo program (PCXMC, STUK, Helsinki, Finland) was used to calculate the effective dose from the DAP values of each patient. Organ doses were also measured with thermoluminescent dosimeters (TLDs) using a human-shaped phantom. The difference between the organ doses measured using TLDs and PCXMC was not significant (P > 0.05). The mean DAP for 48 patients was 9.41±2.50 Gy·cm2; the mean effective dose for all procedures was 0.30±0.08 mSv. The coefficient for the correlation (R2) between the DAP and the effective dose was 0.97. The conversion factor between the effective dose and DAP was 0.030-0.035 mSv·Gy(-1)·cm(-2). DAP can be used as a dose indicator to calculate the organ dose and effective dose of patients based on Monte Carlo simulation. This method can provide important information on the absorbed dose and enhance the radiation protection of patients during C-arm CT procedures.

Consolidation of Hepatic Arterial Inflow by Embolization of Variant Hepatic Arteries in Preparation for Yttrium-90 Radioembolization

Purpose Before yttrium-90 ( 90Y) radioembolization administration, the authors consolidated arterial inflow by embolizing variant hepatic arteries (HAs) to make microsphere delivery simpler and safer. The present study reviews the technical and clinical success of these consolidation procedures. Materials and Methods Preparatory and treatment angiograms were retrospectively analyzed for 201 patients. Variant HAs were coil-embolized during preparatory angiography to simplify arterial anatomy. Collateral arterial perfusion of territories previously supplied by variant HAs was evaluated by digital subtraction angiography (DSA), C-arm computed tomography (CT), and technetium-99m ( 99mTc)–macroaggregated albumin (MAA) scintigraphy, and by follow-up evaluation of regional tumor response. Results A total of 47 variant HAs were embolized in 43 patients. After embolization of variant HAs, cross-perfusion into the embolized territory was depicted by DSA and by C-arm CT in 100% of patients and by 99mTc-MAA scintigraphy in 92.7%. Uniform progressive disease prevented evaluation in 33% of patients, but regional tumor response in patients who responded supported successful delivery of microspheres to the embolized territories in 95.5% of evaluable patients. Conclusions Embolization of variant HAs for consolidation of hepatic supply in preparation for 90Y radioembolization promotes treatment of affected territories via intrahepatic collateral channels.

Embolization of Parasitized Extrahepatic Arteries to Reestablish Intrahepatic Arterial Supply to Tumors before Yttrium-90 Radioembolization

Purpose To perform embolization of parasitized extrahepatic arteries (EHAs) before radioembolization to reestablish intrahepatic arterial supply to large, peripheral tumors, and to evaluate the technical and clinical outcomes of this intervention. Materials and Methods Among 201 patients retrospectively analyzed, embolization of 73 parasitized EHAs in 35 patients was performed. Most embolization procedures were performed during preparatory angiography using large particles and coils. Digital subtraction angiography (DSA), C-arm computed tomography (CT), and technetium-99m macroaggregated albumin ( 99mTcMAA) scintigraphy were used to evaluate the immediate perfusion via intrahepatic collateral channels of target tumor areas previously supplied by parasitized EHAs. Follow-up imaging of differential regional tumor response was used to evaluate microsphere distribution and clinical outcome. Results After embolization, reestablishment of intrahepatic arterial supply was confirmed by both DSA and C-arm CT in 94% of territories and by scintigraphy in 96%. In 32% of patients, the differential response of treatment could not be evaluated because of uniform disease progression. However, symmetric regional tumor response in 94% of evaluable patients indicated successful delivery of microspheres to the territories previously supplied by parasitized EHAs. Conclusions Reestablishment of intrahepatic arterial inflow to hepatic tumors by embolization of parasitized EHAs is safe and effective and results in successful delivery of yttrium-90 microspheres to tumors previously perfused by parasitized EHAs.

Usefulness of C-arm CT during superselective infusion chemotherapy for advanced head and neck carcinoma

To evaluate the usefulness of C-arm computed tomography (CT) during superselective intra-arterial infusion chemotherapy for advanced head and neck carcinoma. C-arm CT was performed during superselective intra-arterial infusion chemotherapy for 11 patients with advanced head and neck carcinoma located in the hypopharynx (n = 3), maxillary sinus (n = 3), oropharynx (n = 1), larynx (n = 1), extra-auditory canal (n = 1), tonsil (n = 1) and tongue (n = 1). The usefulness of C-arm CT during superselective catheterisation was evaluated. On arteriography, nine tumours showed tumour stains and two in the oropharynx or tonsil showed no obvious tumour stains. C-arm CT was performed one to four times (mean ± standard deviation, 2.5 ± 0.8) in each patient during a single procedure. C-arm CT clearly showed not only the vascular territory of the selected branch but also the tumour itself in all patients. Intra-arterial infusion chemotherapy was performed through one to three branches (mean, 1.7 ± 0.9) according to C-arm CT findings without any complications. C-arm CT during superselective intra-arterial infusion chemotherapy was useful to determine the arterial supply of head and neck carcinoma. C-arm CT may replace conventional CT during superselective arteriography in this procedure.

Intraprocedure Visualization of the Esophagus Using Interventional C-arm CT as Guidance for Left Atrial Radiofrequency Ablation

During radiofrequency catheter ablation for atrial fibrillation, the esophagus is at risk for thermal injury. In this study, C-arm computed tomography (CT) was compared to clinical CT, without the administration of oral contrast, to visualize the esophagus and its relationship to the left atrium and the ostia of the pulmonary veins (PVs) during the radiofrequency ablation procedure. Sixteen subjects underwent both cardiac clinical CT and C-arm CT. Computed tomographic scans were performed on a multidetector scanner using a standard electrocardiographically gated protocol. C-arm computed tomographic scans were obtained using either a multisweep protocol with retrospective electrocardiographic gating or a non-gated single-sweep protocol. C-arm and clinical computed tomographic scans were analyzed in a random order and then compared for the following criteria: (1) visualization of the esophagus (yes or no), (2) relationship of esophageal position to the four PVs, and (3) direct contact or absence of a fat pad between the esophagus and the PV antrum. The esophagus was identified in all C-arm and clinical computed tomographic scans. In four cases, orthogonal planes were needed on C-arm CT (inferior PV level). In six patients, the esophageal location on C-arm CT was different from that on CT. Direct contact was reported in 19 of 64 of the segments (30%) examined on CT and in 26 of 64 (41%) on C-arm CT. In five of 64 segments (8%), C-arm CT overestimated a direct contact of the esophagus to the left atrium. C-arm computed tomographic image quality without the administration of oral contrast agents was shown to be sufficient for visualization of the esophagus location during a radiofrequency catheter ablation procedure for atrial fibrillation.

Contrast-Enhanced C-Arm CT Evaluation of Radiofrequency Ablation Lesions in the Left Ventricle

The purpose of this study was to evaluate use of cardiac C-arm computed tomography (CT) in the assessment of the dimensions and temporal characteristics of radiofrequency ablation (RFA) lesions. This imaging modality uses a standard C-arm fluoroscopy system rotating around the patient, providing CT-like images during the RFA procedure. Both cardiac magnetic resonance (CMR) and CT can be used to assess myocardial necrotic tissue. Several studies have reported visualizing cardiac RFA lesions with CMR; however, obtaining CMR images during interventional procedures is not common practice. Direct visualization of RFA lesions using C-arm CT during the procedure may improve outcomes and circumvent complications associated with cardiac ablation procedures. RFA lesions were created on the endocardial surface of the left ventricle of 9 swine using a 7-F RFA catheter. An electrocardiographically gated C-arm CT imaging protocol was used to acquire projection images during iodine contrast injection and after the injection every 5 min for up to 30 min, with no additional contrast. Reconstructed images were analyzed offline. The mean and SD of the signal intensity of the lesion and normal myocardium were measured in all images in each time series. Lesion dimensions and area were measured and compared in pathologic specimens and C-arm CT images. All ablation lesions (n = 29) were visualized and lesion dimensions, as measured on C-arm CT, correlated well with postmortem tissue measurements (linear dimensions: concordance correlation = 0.87; area: concordance correlation = 0.90. Lesions were visualized as a perfusion defect on first-pass C-arm CT images with a signal intensity of 95 HU lower than that of normal myocardium (95% confidence interval: -111 HU to -79 HU). Images acquired at 1 and 5 min exhibited an enhancing ring surrounding the perfusion defect in 24 lesions (83%). RFA lesion size, including transmurality, can be assessed using electrocardiographically gated cardiac C-arm CT in the interventional suite. Visualization of RFA lesions using cardiac C-arm CT may facilitate the assessment of adequate lesion delivery and provide valuable feedback during cardiac ablation procedures.